For instance, as for point of sale (POS) machines and automated teller machines (ATMs) widely applied in the banking system and the business system, users can receive required service after entering a password or passwords.
A traditional password input device generally employs mechanical keys as function keys. By adoption of the mechanical keys as the function keys, the character specified on each function key for password is unchangeable, and hence the arrangement mode of the characters is unchangeable. Thus, observers not having a password can easily analyze the password entered by a password inputter according to the gesture of the password inputter for operating corresponding function keys. Therefore, the password input device has large security risk if the characters on the function keys for password are arranged in an unchanged arrangement mode.